1. Field of the Invention
The invention relates to a method for driving an organic light emitting display (OLED) panel, and more particularly to a pulse width modulation (PWM) method for driving an OLED panel.
2. Description of the Related Art
FIG. 1 shows a schematic view of a conventional OLED 100. The OLED 100 comprises a plurality of segment lines 122, a plurality of common lines 132, a plurality of organic light emitting diodes 112, a segment driver 120 and a common driver 130. The organic light emitting diodes 112 are positioned on an OLED panel 110 and are electrically connected to the segment lines 122 and the common lines 132 in a matrix structure. The organic light emitting diodes 112 of one common line 132 are divided into a first group 142 and a second group 144. The segment driver 120 is electrically connected to the segment lines 122 and supplies driving currents to the organic light emitting diodes 112 of the first group 142 and the second group 144 separately according to a first PWM manner and a second PWM manner. The first PWM manner and the second PWM manner have complementary waveforms in a period.
FIG. 2A shows a schematic view of waveforms provided by the first PWM manner of the OLED 100, and FIG. 2B shows a schematic view of waveforms provided by the second PWM manner of the OLED 100. FIG. 2A and FIG. 2B use the waveforms GS1 to GS4 of 2-bit grayscales as an example to show that the first and the second PWM manners have complementary waveforms in a period T. In FIG. 2A, the rising edges of the waveforms GS1 to GS4 corresponding to different grayscales are all positioned at a starting time t0 of the period T. In FIG. 2B, the falling edges of the waveforms GS1 to GS4 corresponding to different grayscales are all positioned at an ending time t4 of the period T.
Referring to FIG. 2A, the rising of the waveforms GS1 to GS4 causes a peak current to be generated at the starting time t0 of the period T. The peak current increases the required Vcc of the segment driver 120 shown in FIG. 1, and the power consumption of the OLED 100 is thus raised. Referring to FIG. 2B, the falling of the waveforms GS1 to GS4 causes the current to be decreased at the ending time t4 of the period T. The current decreases the required Vcc of the segment driver 120 shown in FIG. 1, and the power consumption of the OLED 100 is thus fallen. Therefore, in the OLED 100, the power consumption measured at the starting time t0 and the ending time t4 of the period T is extremely strong when the amount of the organic light emitting diodes 112 of the first group 142 and the second group 144 is increased, wherein the extremely strong power consumption will decrease image quality of the OLED 100.